The present invention relates to a bicycle free wheel assembly, and more particularly to an improvement in a multi-speed bicycle free wheel assembly having a plurality of sprocket wheels which are different in diameter and are arranged in parallel to one another.
As is well known, a multi-speed bicycle free wheel assembly is externally installed on one end of a rear wheel axle of a bicycle so that it can cooperate with a rear derailleur to facilitate a desired speed change of a bicycle. It has been observed that a running drive chain of a bicycle may be unexpectedly disengaged or fall out of the smallest sprocket wheel (top gear) which is disposed outmost of the free wheel assembly, when the running chain is shifted from a lower gear to the top gear, viz., from one of the larger sprocket wheels to the smallest sprocket wheel under the known chain-swing operation of the rear derailleur. And serious accidents and bodily injuries to riders have been attributed to such disengagement of the running chain from the free wheel assembly during cycling.
In eliminating the above-mentioned deficiency, it has been apparent to those skilled in the art that the undesirale disengagement of the running chain can be prevented by provision of a proper chain fall preventing device in position near the outward surface of the smallest sprocket wheel. In fact, several kinds of chain fall preventing devices such as a finger type, a nail type, a semi-circular disc type, a hook type or the like have been proposed. Such conventional chain fall preventing devices are of two varieties. The first group are those in the form of a separately-made piece to be fixedly secured to a suitable portion of a shifter body or in the vicinity of a rear derailleur or to a derailleur mounting bracket with one or more mounting screws. The second group are those in the form of an integral part which offsets or extends from a certain portion of the shifter body, a pulley cage or other parts of a rear derailleur or from a rear derailleur mounting bracket. However, all such conventional chain fall preventing devices are designed for use only in a specific bicycle of a certain manufacturer and therefore cannot be applicable to other bicycles produced by other manufacturers. Further, it may not be easy to incorporate a conventional chain fall preventing device with a rear derailleur or near its vicinity because most of the conventional devices are rather intricate in construction, and postion adjustment is usually required so that a chain fall restricting surface of the conventional device may face operatively toward the outward surface of the smallest sprocket wheel of a free wheel assembly because some conventional devices are not symmetrical in configuration. Further, none of the conventional chain fall preventing devices are designed to cover the total outward surface of the smallest sprocket wheel due to the fact that they are not easily accessible thereto since they are provided not with a free wheel assembly per se but with a rear derailleur or with a rear derailleur mounting bracket. Still further, most of the conventional chain fall preventing devices may not be easy to manufacture and thus are not low in cost due to their peculiar configuration. Furthermore, the conventional chain fall preventing devices in the form of a separately-made piece have a disadvantage that an extra process is required in assembling. Also, those in the form of an integral part formed with a rear derailleur or with a derailleur mounting bracket or the like have a fatal disadvantage, when the chain fall preventing device itself is broken or damaged, the whole assembly must be changed, which is very uneconomical.
According to the present invention, the chain fall preventing device is incorporated with a bicycle free wheel assembly per se. More particularly, the chain fall preventing function is performed by an annular flange which is formed with a known screw cup of a free wheel assembly. The smooth inward surface of the flange may be positioned with a certain small space from the outward surface of the smallest sprocket wheel of the free wheel assembly.
It is, therefore, a principal object of the present invention to provide an improved and novel multi-speed bicycle free wheel assembly having a device for preventing a drive chain from being accidentally disengaged outwardly from the smallest sprocket wheel.
Another object of the invention is to provide a multi-speed free wheel assembly which is designed to prevent a drive chain from falling out of the smallest sprocket wheel without increasing the number of elements or pieces of a free wheel assembly.
A further object of the invention is to provide a multi-speed free wheel assembly which carries out a desired chain fall prevention without any change to a conventional assembling process.
A still further object of the invention is to provide a multi-speed free wheel assembly having a chain fall preventing device which can be easily incorporated with the free wheel assembly without position adjustment.
A yet further object of the invention is to provide a multi-speed free wheel assembly having a chain fall preventing device which is more effective than any other conventional chain fall preventing devices.
The above and other objects, features and advantages of the present invention will become more apparent from the following description of one of the preferred embodiment thereof taken in conjunction with the accompanying drawing.